About my job in hk, options?

First of all:
What is ur highest degree? field of profession? what did u study back in Australia? and what is the work experience u gained there? were u saying u like to do customer service as a life-long profession?
Secondly:
Grade D in any subject doesn't look so good, and probably wouldn't help u internationally. 7.5 Ielts is pretty average as well, so in conclusion, you may not be able to use your language skills for job of translation, but there is a chance for u to work or study abroad (in other english-speaking country of course).
Last but not least:
What do you want to do with your life? How do you feel about going back to school?
The hurtful truth is you really need some sort of degree/certificate or years of professional experience for 9-6 employment.

You need to offer a lot more info here. If you continue working the minimum wages, it might earn you tuition fee you needed in 5-6 years. There is no easy start, it's not that simple. People can get a bachelor with straight As still have trouble finding a 9-6 job.

Unlikely to happen.

Merely studying in a foreign country is not sufficient for any international firms to have an interest on you.